Intermediate telegraph repeater for long line spans



\ 1947. R. B. HEARN ET A1. 2,422,677

INTERMEDIATE TELEGRAPH REPEATER FOR LONG LINE SPANS June 24 Filed July 1, 1944 2 Sheets-snee?I l hun atm: z2

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IN VEN 7' ORS `A fr0/wey June 24, 947.`

R. B. HEARN ET AL INTERMEDIATE TELEGRAPH REPEATER FOR LONG LINE SPANS Filed July l, 1944 2 Sheets-Sheet 2 N GSK Patented .une 24, i947 INTERMEDIATE TELEGRAPIRETER FOR LONG LINE SPANS Richard B. Hearn, Hollis, N. Y., and Carleton B. Sutli, East Orange, N. J., assignors to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York.

Application July 1, 1944, Serial No. 543,112I

1 This invention relates to telegraph systems and particularly to an improved direct current telegraph intermediate repeater capable of receiving from one telegraph line section and retransmitting to another telegraph line section.

An object of the invention herein is the improvement 'of telegraph repeaters. A more specic object of the invention herein is the improvement of intermediate telegraph repeaters so as to insure satisfactory operation on lines of very long span. Another more specific object of the invention is the provision of local communication and monitoring facilities for an intermediate Atype B polarential repeater.

The improvements herein are shown applied to what is known in the art as a type B pol-arential telegraph repeater system. Such a system is disclosed in the patent to W. W. Cramer 2,131,870, October 4, 1938. The principles yof operation of the type B polarential repeater system to which Y the invention herein is applied will be described sufficiently so that the manner in which the invention herein cooperates with such a system may be better understood.

The improved intermediate repeater herein provides half duplex loperation only. The improvement consists in part in the addition of a monitoring feature to 4an intermediate repeater in a type B .polarential repeater system.

The repeater herein is designed for operation on simplexed elcl wire line circuits, composited or simplexed open wire and simplexed cable facilities with ground return.

The repeater herein contains a built-in rectifier power unit. It is contemplated that a teletypewriter transmitter and receiver will ordinarily be used with the monitoring facilities. A manual telegraph set integral with the repeater equipmentis furnished for use when teletypewriter equipment is not availablefor service.

The line sides of the repeater are arranged to employ the type B polarential, polar-receiving form of transmission.

The local side of the repeater is arranged for operation with 4a sending and receiving teletypewriter or a manual telegraph set.

A feature of the invention is an improved monitoring circuit for use with an intermediate repeater. f

A further feature of the invention is an improvedanti-kickoi feature for use in an intermediate repeater arranged for operation on lines of exceedingly high electrostatic capacity. 1

A further feature of the invention is a cutting feature arranged to permit communication from 12 Claims. (Cl. 178-71) 2 the monitoring circuit through the intermediate repeater over one line section when the opposite line section is out of service due to trouble, etc.

A further feature of the invention is an improved power supply arrangement -adapted to convert Apower from a number of different types of sources to power of the characteristics required by the apparatus herein so that the repeater may be readily usuable under different conditions encountered in the eld. Y,

yA further feature of the invention is a circuit which develops a characteristic tone forV use with one form of telegraph signal receiver incorporated in a monitoring circuit associated with an intermediate repeater. p I' The operation of a system embodying these and other features will become apparent from the following description when read with reference to the associated drawings herein in which Fig. 1 shows the improved intermediate repeater of the invention. Fig. 2 is a vcircuit used in explaining the principles of operation of a type B polarential telegraph circuit with which the improved intermediate repeater herein is designed to cooperate. Figs. 3 and 4 are diagrams usedin explaining the advantages of the type B polarential system per Fig. 2,

GENERAL.

^ Before proceeding with a detailed description of the inventionrherein, the invention will iirst` be described in a general way so that the detailed operation may be better understood.

It is to bey understood that the invention herein Vis shown as applied to an intermediate repeater Fundamentally a circuit operating on a polarential basis employs polar transmissi-on in one direction and diierential transmission in the other direction. These two terms have been combined to form the term polarential. 'In a polar transmissionv system the marking and spacing line currents are of the same magnitude and ilow in opposite directions, and hence the receiving relay to the intermediate repeater 205 in the same manner as is the distant terminal repeater A and the operation of the circuit when repeater B transmits toward the intermediate repeater is the same yas described for the condition wherein repeater A transmits towards the intermediate repeater. A v

Reference to Fig. 3 shows the effect of weather conditions upon the marking and spacing signals received at the intermediate repeater. When the weather is dry the marking and spacing signal current is 18 milliamperes. When the weather is wet the received currents may be of any value less than 18 milliamperes, but they will be equal for each condition. Under the condition indicated in Fig. 3, it is assumed that milliamperes is being received for each signal for a particular Wet condition. f

Intermediate 'repeater sending to terminal A or terminal B The manner in which the intermediate repeater retransmits signals received from one terminal repeater toward the other terminal repeater will now be described. It will be assumed that terminal repeater A is transmitting toward the intermediate repeater' and it will be explained how the intermediate repeater retransmits the signals `received from repeater A to terminal repeater B and how terminal repeater B responds to the received signals. f

In response to signals received from terminal repeater A the yarmature of receiving relay 206 in the intermediate repeater is actuated between its opposed contacts 2I0 and 2| I; For the'mark-` -ing condition the armature of relay 206 in the intermediate repeater engages its marking contact 2I0. The armature of sending relay 2I3'at the distant terminal repeater B will be maintained in engagement with its marking contact 2I4 under the influence of the current iiowing in its winding 2I5. Acircuit may then be traced from ground through marking contact 2I0 of relay 20E and the winding of relay 201 to line 2|6 which extends from the station at which the intermediate repeater is located to the station where the `distant terminal repeater B is located. The circuit continues through the top or' line winding of receiving relay 2I2 at the distant terminal repeater 'Band through the armature and marking contact 2l 4 of relay 2 I 3 to negative 57%?, volt battery and thence to ground. When-the armature of relay 206 engages its spacing contact 2II positive 115-voltbattery is connected `to the circuit just traced.

If it is assumed that the direction of the iiow of the current is from the point of higher positive potential toward the point of negative potential, when the armature of relay 206 is in engagement with its marking contact 2I0, the direction of the ow of current is from the'intermediate repeater toward the distant terminal repeater B. When the armature of relay 206 engages its spacing contact 2l I the positive 115-volt battery connected to contact 2|I is in a series aiding relationship withV the negative 571/2-volt battery connected to the marking contact of relay 2I3 at terminal repeaterY B. The direction. of theV flow of current will therefore remainunchanged', although vits magnitude is increased. The armature of relay 201 will be maintained in Vengagement with its -markingcontact 208V by the effect-)of each'oi lthese currents, each of which f tends to actuate the. armature towards its marking-contact 208. lIn'the ycase'of receiving relay amat??- and the direction of the current in the line wind ing of relay 2i 2 is the same asfor the marking condition, its effect tending to actuate the armatureof relay'2 I 2 towards its spacing contact is increased and the effect in the upper or line winding becomes dominant so that the armature of relay 2I2-is actuated to engage its spacing contact. I

AThe total voltage applied to the line 2I6 during the marking interval is 571/2 volts and during the spacing interval is 1721/2 volts, which is three times the voltageapplied tothe line ,during the marking interval. Therefore, the spacing line current is three times the marking line current when the intermediate repeater issending. For a dry line condition these currents are 18 milliamperes for marking and 54 milliamperes for spacing.

vRefer now to Fig. t4. This figure indicates how the signals received from the intermediate repeater at the terminal repeater arenot biased as a result of changes in Weather conditions. The current in the lower or biasing winding of the receiving relay such as 2I2 is supplied from a local battery at each terminal. For the constants which are assumed, its magnitude is xed at 36 milliamperes which is half of the sum of the marking and spacing signal'current. When the weather is wet the veffect is as though a resistance were connected between the line 2 I6 and ground. Thus the magnitude of the spacing current flowing through the topwinding of relay 2 I 2 when the two batteries are in series will be decreased.

Assuming that the resistance of each repeater is equal, the voltage at the center of the line would be negative 28% volts during the marking interval and positive 28% volts during the spacing interval. Therefore, the current through the leakage path would be approximately the same magnitude for the marking or spacing condition if the leakage is lumped at the center or uniformly distributedover the line. Thus if the leakage current is about 4 milliamperes, the marking current in the upper Winding of relay 2 I 2 is increased by that amount and the spacing current is de* creased an equal amount. Under such a condition the magnitude of the spacing current will be 50 milliamperes and the magnitude of the marking current will be 22 milliamperes. The sum of these two currents is still '72 milliamperes as before and the magnitude of the biasing current of coursek remains 36 milliamperes. The diierence therefore between the magnitude of the biasing current and the magnitude of the spacing current remains the same as the difference between the magnitude of the biasing current and the magnitude of the marking current and the receiving relay 2I2 responds without bias to the signal elements regardless of changing weather conditions.

f In transmitting from the intermediate repeater 205 towards terminal repeater A the operation is termedate repeaterl 2.05 towards 'terminal rcpeater The invention herein is an improved, intermediate repeater whichserves the same purpose as the intermediate repeater 205 in the system per Fig. 2 described above. The improved. repeater is .shown in Fig. l. The .improvements .as mentioned above lconsist chiefly in the provision of, (1) a monitoring circuit arranged to cooperate with such :an intermediate `rglepeater as is shown in Fig. 2, V 2) an 4anti-kicltorf feature which permits the intermediate repeater of the invention herein to function with lines subject to very heavy cur-rent surges due to very high capacity between the line and ground, without preventing its use on V lines yof low capacity and (3) improved power suppl-y facili-ties which adapt the intermediate repeater herein for operation with a variety of power supply 'arrangements v such as are encountered by portable telegraph repeaters in the field. v

IMPROVED INTERMEDIATE REPEATER Refer nowto Fig. 1. In this vfigure an inter.- mediate repeater is Shown in which thebasic transmission features are `the same as described for intermediate repeater 2.05 per Fig. 2 but the repeater is equipped with a special monitoring circuit, .an improved anti-kickoff .circuit and -an improved power supply circuit.

In Fig. 1, .lines and .|02 correspond to lines 2.01% and .2|6, respectively, in Fig. .2 and 4extend to distant terminal repeaters corresponding to distant terminal repeaters A and B, respectively in Fig. .2. Relay .|03 .corresponds to relay 205 and relay .|04 .corresponds .to relay 201 in Fig. 2. Two new relays, ,sending .relay |05 and receiving relay ligbothof which function in the improved monitoring .circuit,'have been added to the intermediate repeater. `In the case oi relays 206 and 201 in Fig. 2 there was but a single winding, namelygthe `line winding, on each ofthe relays. Relays |03 and |011 each have two additional windings. In addition lto the top or line winding on each of these relays, the two lower -wind ings of each-are connected in an improved antiekickof circuit comprising the two windings, two resistances such as |01 and Ill, two rectifier units such as |08 and |09, a condenser -such as 4Htl, and the inductance coil '90 all of which are Vassociated with the anti-kickoff circuit of relay The .intermediate repeater per Fig. 1 may be arranged so that the monitoring facilities are in effect disconnected. Such is the condition when no apparatus is connected to any of the three jacks, Il, IS ,and .I1-9 shown at the lower right -of the figure. The monitoringcircuit is arranged to function either with teletypewriter facilities `such as the receiving .teletypewriter apparatus, indicated by the Yreceiving magnet |2i3, and the iteletypewriter transmitting apparatus, indicated ,by ,the transmitting contacts .i12-i, orwith a manual telegraph transmitting key anda `telephone Aheadset receiver such vas |22 and |23, respectively. All of this apparatus is .well known in the art. :When ,no apparatus is connected .to jacks ;|i;'|, V|||l and "H9, which is the condition shown in the drawing, the circuit per Fig. 1 is .arranged to function as an intermediate repeater -without monitoring facilities As stated above, the circuit per Fig. 1 is arranged to function with various power .supply carrangements. For .the present it .will be .assumed that :the circuit is V.to "function Vwith `a 1^15-.vo1t v;

direct current .supply-ia whichcasc the potrei circuit included rectangle |25 Pelecrms 110 function.. Key |24 Ais actuated sc as to engage its upper cantacts- The negative terminal ci the 11e-veit .direct current supply is connected to arcane l|26 thrcueh contacts |21 and |23 ci key |24 to the negative terminal of the 11d-volt direct current aucply- From the positive ter- Initial ci the 115-'ve1t direct current Supply a circuit may be traced through fuse |29, contact L30, contact |3| and fuse |32 to bus bar |33 from which point parallel branches extend. One branch vextends through resistance |;-l||V to spacin g contact |35 of relay v| 03 and spacing contact ,|136 of relay |04, A circuit may also be traced .frcm arca-11d .|31 thrcush contact |38 cf Key |22, contact |39 .o f Yjack AI I1 and thrcugh the inductance coil |40 of filter Ml'to -marking contact 1l2 of relay 3 and marking contact -|03 of relay |04. Frornthis it may be seen Vthat the battery conditions connected to the marking and spacing contacts .of relays |03 ,and m4 are the same as for the .corresponding relays in intermediate repeater 2.05 in Fig.

It was .explained above that the distantend of the line 204 in Fig. -2 which .corresDOnds to line 01| in Fig. 1 is connected to negative 5 71a-V01t battery "for the riflarkirig condition. A circuit may be traced in the intermediate repeater per Fig. -1 ,through inductaacc -.l 4||y 0i Vfilter |45. inductance |46, top or line winding Vof relay |03, con` tact .|41 0i the l3-cutz1ine .key .and` through the .armature cf -`relay |04 which is in engagement with its marking yccntact M3 -frcm which point the circuit has been traced tc sroand- On the opposite side of :the repeater line |02 which cor.

responds te line ZIB in Fef2 'iS terminated 'at the distant v-terir1ir1-a1 repeater lB inneeatve 571/2- volt battery. The .circuit may be traced in the intermediate repeatcrpper Fie. 1 through inductance |48 of lter |49, inductance L50, top or line Winding .ci relay |04..

:line key and the armature .o f relay |03 which is inengagement w1th its .marking Contact |42 from .which Peint thecifcuit bacheca tracedtc ercand 4.311. The effectci-the anti-kickoff circuits will be described V.hercinafter .Dieregardingthis ciiect,..which tends to Acounteract .heavy line current surges, relays |03 `and =|04 vwill operate in :the .Same manner as .described .above fcr relays n 2.0.6 and 20] in the intermediate -repeatergq per Fig. 2.

" Monitoring vrcircuit The manner in Awhich the -monitoring circuit functions will now be described. #It -w-ill be as- -sumed .that .the teletypewriter. monitoring Afacilities are to be employed. rThe teletypewriter Atransmitter and .receiver are each equipped with acord and a plug so that `t-hey may beconnected vto and disconnected from rjacks in 'the-monitoring circuit. When the teletypewriter transmitter -and receiver are .to be used for monitoring, plug |52 -isconnected .to jack 1| |.8 `to interconnectthe `teletypewriter transmitter |2| and the fmonitor- .ing circuit and plug |53 `is connected to jack .to-interconnect -lthe vtypewriterreceiver |20 and xthemonitoring circuit. vWhen `plug |53 :is yin- .;serted :in jack .contact .|39 :is Aopened, and contact 1|;1.| is closed. .This Vtransfers the path .supplying ground .|31 Vtothe intermediaterepeater `to I a .pathfthat vextends through .the armature of relay l 0 5V and its :marking .contact .fl 'l2 to ground 111.4. 4Acirouit may now be tracedrromthe positive :bus baril-.id through resistance. f|55,bottom f-windingof relay 105, inductance .|56 .offilter 151,

L9' tip of jack ||8, tip of transmitting contacts |58, ring cf plug |52, and the ring of jack ||8 to ground |59. A circuit may also be traced from the positive bus bar |54 through resistance |60, top winding of relay 05, contact |6| of jack 8, bottom winding of relay |06, and contact |63 of jack 8 to ground. The rst of the above two paths extended through the bottom Winding of relay and the second extended through the top-winding of relay |05. The effect of the current flowing through the bottom Winding of relay |05 tends to actuate an armature of relay |05 to engage with its right-hand or marking `Contact and when teletypewriter contacts |2| are closed, this effect is dominant over the effect of current iiowin`g in the top winding of relay |05 which tends to actuate the armature of relay |05 toward the left to engage with its spacing contact. When the teletype- Writer transmitting contacts |2| are open, the circuit through the bottom winding of relay |05 is deenergized and the armature of relay |05 is actuated to close its spacing contact under the influence of the current in its upper winding. The eifect of the current flowing through the bottom Winding of relay |06 tends to actuate the armature of relay |06 to engage with its righthandor marking contact'.

From junction point |64 in the path extending toward the distant repeater A, a branch extends through resistance |66, top winding of relay |06, resistance |61 and contact |63 to ground. From junction point |65 in the path extending toward the distant repeater B, a branch extends through resistance |68, middle winding of relay |06, resistance |62 and contact |63 to ground. When the distant terminal repeaters are terminated in negative battery for the marking condition, there is no current flowing in each of the two upper windings of relay |06, since the paths from junction points |64 and |65 through each of the two upper windings of relay 06 are shunted by a path to ground which has been traced in the main repeater circuit. For the marking condition therefore the current in the lower winding of re lay 06 is holding the armature of' relay |06 on its marking contact.

It will be assumed that the armature ofy the sending relay in distant terminal repeater A impresses positive battery on line |0| totransmit a spacing signal toward the intermediate repeater. As explained above, the voltages mpressed on line |0| at the distant terminal are equal in magnitude and of opposite polarity for the marking and spacing conditions. The effect o1 the current of reversed polarity in the top winding of relay |03 operates the armature of relay 03 to its spacing contact. Operation of relay |03 to its spacing contact removes ground and applies positive l15-volt battery to junction point |65. This causes a current to o'vv in the middle Winding of relay |06 which is poled in such a manner and is of sufiicient magnitude to overcome the effect of the current flowing in its lower winding, thus operating thearmature to spacing contact |10. When the armature of relay |03 is again actuated to engage its marking contact |42, the conditions prevailing originally in all three windings of relay |06 will be reesta'blishedv and its armature Will again engage its marking contact'.

As the armature of relay |06 follows the received signals, ground connected to' the armature is alternately connected to and disconnected from the Ecircuit extending through the winding of the lug |52, teletypewriter receiving magnet |20. This circuit may be traced forthe marking condition from positive battery at bus bar |54through resistance |15,'inductance |16 of iilter |11, tip of jack ||1, tip` of plug |53, winding ofthe teletypewriter Yreceiving magnet |20, sleeve of vplug |53, sleeve of jack ,||1, inductance |18 of lter |11l and the marking contact |69 of receiving relay |06 to ground energizing magnet |20. When marking contact |69 .is opened, the receiving magnet |20 is deenergized.

The manner in which signals are transmitted from the teletypeawriter transmitter |2| Will'noW ybe described. It was explained above that as the teletypewriter lcontacts |2| were opened and closed, the armature of relay |05 was actuated so as to follow the signals. When the armature lof relay |05 is in engagement with its marking'contact |12, ground |14 is connected through contact |12 to marking contacts |42 and |43 of relays |03 and |04, respectively. The path has heretofore been traced. -When teletypewriter |2| is trans-r mitting, the armatures of relays |63 and |04 remain in engagement with their respective marking contacts. Thus, ground for the marking condition is impressed on lines 02 and |0| simultaneously. When a spacing signal is transmitted from sending relay |05, the armature of relay |05 is actuated to engage its spacing contact |13. Spacing contact |13 is connected tothe 115-volt positive battery bus bar |54 through resistance |34. Positive -volt battery'is thus impressed through marking contacts |42 and |43 of relays |03 and,|04 on lines |02 and |0| totransmit a spacing signalto the distant terminal repeaters A and B simultaneously. -1

Cutting feature The intermediate repeater herein includes a cutting feature to facilitate the location of trouble and to" permitv limited communication while trouble' conditions prevail. It will be assumed that plugs |52 and |53 remain inserted in jacks 3 and ||1 respectively. When the circuit to distant terminal repeater AA appears to be in trouble, -cutline A key may be operated to its alternate position in order to establish communication with distant terminalA repeater B. Operation of cutline key A disconnects the line Winding of relay A|04 from the armature of relay |03, through Athe opening of contact |5| and connects it'directly, through contact |19, conductors |8| and |82, to the armature of relay |05. In response to the operation of transmitter |2|, ground for marking and 1-15volt positive battery for spacing will be connected through the contacts of relay |05, contact |11, inductance |40 of lter I 4|, conductors |82 and |8|, contact |10 and the top winding of relay |04 to line |02. Simultaneously, the same signalswill also be impressed on line |0| through the normal path for Atransmission from the monitoring circuit which has been traced through the marking contact of relay |04. If the circuit t distant terminal repeater Bl cannot be established and communication to distant terminal A is satisfactoryv cut line B key may be operated to open contacts |41 and close contacts |80. This disconnects the armature of relay |04 in a manner similar to that just described for cut key A. Signals may then be impressed on line |0|"from the contacts of relay v|05 through contact' |1|, inductance |40 of lter |4|, conductors |2`anol |83, contacts |80'and through the top Winding 'of' relay '|03 tov line |0|. Simultaneously, the signals will continue to be transmitted to line |02 through marking contact |42 of relay |03. As soon as the circuit is reestablished bothv cir- 13 vWhen the armature of relay 04 engages its spacing contact the potential of junction points |98 and |99 becomes approximately 115 volts positive. Rectifier I 09 is poled so that it passes current from battery Lof positive polarity. The current charges condenser IIO. No current ows through the two antikick-off windings for this condition as rectifier |08 is poled so that it does not pass current due to positive potential applied between junction point |99 and ground. Current flowing through rectifier |09 to the condenser I I could pass through rectifier |08 but junction points |98 and |99 are at the same potential. During the spacing interval line |0I becomes charged. The portion of line |0I adjacent the intermediate repeater per Fig. 1 will be heavily charged positively with respect to ground. When the armature of relay |04 is again actuated to engage its marking contact, line |0| will be grounded. A heavy surge of current due to the discharge of the positively charged line will be conducted from the left-hand to the righthand terminal through the top winding of relay I03. Since positive potential when applied to the right-hand terminal of the top winding of relay |03 tends to actuate the armature of relay |03 to engage its marking contact, the effect of the positive potential applied to the lefthand terminal of the top winding of relay- |03 will tend to actuate its armature falsely to its spacing contact for an interval until conditions become stabilized. The length of the interval will depend on the magnitude and duration of the discharge surge.

The constants of the antikick-oif circuit are so chosen that they produce an effect on relay |03 whichpreponderates over the effect of the kicko surge. When in effect marking ground is connected to junction points |98 and I 99, condenser I|0 discharges. The discharge current cannot ow through rectier |09 as it is so poled that it cannot pass current of positive polarity which will be applied from the left-hand terminal of condenser IIO. Reotier |08 is so poled that it passes current of positive polarity from the left-hand terminal of condenser |I0. The terminals of the two bottom windings of relay I 03 are so connected that the effect of the current flowing through rectifier |08 from condenser I|0 and the two bottom windings of relay |03 invparallel tends to maintain the armature of relay I03 on its marking contact, during the interval while the kick-off current surge persists. Resistance |01 and inductance 90 assist in controlling the rate of discharge of condenser I|0 through the lower windings of relay |03.

The presence of rectifier |08 in series with the lower windings of relay I 03 materially lessens the shunting effect of the condenser |I0 with its discharge circuit, on the windings of relay |03. Without the rectifier |08 this effect would have a very detrimental influence in that it would make relay |03 Very sluggish so that it would not follow the signals received from the line with the same degree of accuracy achieved through the use of rectier |08. This permits operation over lines having appreciably higher capacity than would otherwise be possible.

Power supply circuit Attention was called in the foregoing to the fact that the intermediate repeater per Fig. 1 was arranged to be supplied with power from a number ofv diiferent sources. It has been assumed heretofore that the power was obtained directly from a -volt direct current source. For this condition rectifier circuit |25 was not required and switch |24 was actuated upwardly. The power circuit |25 is arranged so that it can, for example, convert 115-volt or 230-volt alternating current into 115-volt direct current. Further, the power circuit is arranged so that it can convert current from a relatively low voltage direct current source into direct current of a higher Voltage. For instance 12volt direct current may be converted into 115-volt direct current to operate the repeater herein. Conductors I 0 and II may be connected to a 115-volt alternating current or a 23o-volt alternating current, or to a 115-volt direct current supply. If the source is 115 volts direct current, switch |24, as mentioned above, is operated upwardly. Power rectifier circuit |25 is not involved under this condition. Conductor I 0, which is grounded through contacts |28 and |21 at |26, connects to conductor I2 which forms one of the power supply conductors for the teletypewriter transmitter and receiver. Conductor II extends through fuse |29 and contact I4 of switch |24 to conductor I3 to form the other power supply conductor for the printer. 115-volt direct current is furnished as a power supply for the teletypewriter for this condition.

If conductors I0 andv II are connected to a 115-volt alternating current supply switch |24 will be in the position shown. Plug I5 will be inserted in jack IB. iSwitch 33 will be closed to engage its upper contacts 35, 36 and 31. Switch 34 will be closed to engage its right-hand contacts `53, 54 and 55. Conductor I0 connects to conductor I2 which forms one of the two power supply conductors for the printer. Conductor I0 also extends through contact 68, contact I9, contact 22, coil 25 of transformer 5|, the top switch blade of switch 34, Contact 55, fuse 1|, contact 35, middle switch blade of switch 33, contact 42, contact 4I, left-hand switch blade of switch 33, contact 35, contact 20, contact I1, contact 66, and fuse I 29 to conductor II. Coil 29 of transformer 5| is connected in parallel with coil 25 across contacts 20 and 22 through the middle blade of switch 34 and Contact 54. Conductors II and I3 are joined in the following manner: From conductor II, through fuse I 29, contact 66, contact I1, contact 20, contact 35, left-hand blade ofswitch 33, contact 4I, contact 42, middle blade of switch 33, contact 36, fuse 1|, contact v53, bottom blade of switch .34, conv tact 2|, contact I8 and contact 61 to conductor I3. 115-volt alternating current power is supplied to the teletypewriter for this condition. The voltage impressed through Vcoils 25 and 26 in parallel induces a voltage in the secondary 14 of the transformer 5I. Various taps from the secondary of transformer 14 are brought out to contact points on switches 49 and 50. Switch 50 provides a coarse voltage adjustment and switch 49 provides a fine voltage adjustment. The voltage output from the switches is impressed across the input of the rectier bridge comprised of rectifiers 6|, 62, y03 and 94. The rectified output of the rectifier bridge is impressed through contacts y99 and 10 between ground |26 and busbar |54. The constants of the rectier circuit are chosen so as to translate the 115-volt alternating current supply into 115-volt direct current voltage. Shunt condenser `48 and the series inductance filter out any alternating current in the output of the rectifier bridge.

When conductors I0 and are connected to 230-volt alternating current, switch |24 is in the position shown. Plug I is inserted in jack Iii.. Switch 33 is operated to engage contacts 35, 36 and 31. Switch 34 is operated to engage contacts 56, 51 and 58. This results in the connection of coils 25 and 26 in series through the two top blades of switch 34 across the contacts 25 and 22 across which the ZBO-volt alternating current is impressed over a circuit which should be obvious from the foregoing. Coils 23 and 24 of autotransformer 52 are also bridged across the 230- voli'l alternating current supply contacts 29 and 22. A tap from the mid-point of these coils supplies 115-volt alternating current Voltage to the teletypewriter for this condition, over a path through the bottom blade of switch Sli to contact 2 I, from which point the circuit has been traced to lower conductor I3 of the printer power supply circuit. When coils 25 and 26 are connected in series across a ZBO-volt alternating current power supply the output between ground and busbar |54 is 115-volt direct current voltage as formerly.

When a 12-Volt direct current power supply is used the teletypewriter is not used and no power is supplied to conductors I2 and I3. The 12-volt direct current is translated into 115-Volt directcurrent in the following manner. Switch I2 is in the position shown. Plug I5 is not connected to jack I5. Switch 34 stands open as shown. Switch 33 is actuated to engage contacts 38, 39 and 40. The 12-volt direct current supply is connected across contacts 59 and 69. A circuit may now be traced from contact 69, through fuse 44, contact 38left-hand blade of switch 33, contact 4I, contact 42, middle blade of switch 33, contact 40 and inductance coil 45 to junction point 'i5 where parallel branches are formed. One branch extends through contact 40, right-hand blade of switch 33, contact 43, winding 29 of vibrator 16 and contact 32 to contact 59. The second branch extends from junction point, 15 to the mid-point of coils 21 and 28 of transformer 5I. When contact 30 is closed the circuit continues through coil 21 and contact 30 to contact 59. Coil 21 is energized. Winding 29 is energized actuating armature 11 to open Contact 39 and close Contact 3l. Coil 28 is energized and its eiiect is in a direction the reverse from that of coil 21 when coil 21 was energized. When contact 32 opens magnet 29 is deenergized to reestablish the original circuit. The result is the impressing of an alternating voltage on the secondary 14 of transformer 5I which is translated into 115 volts direct current and applied between bus-bar |54 and ground.

What is claimed is:

1. In a direct current telegraph system, a pair of terminal telegraph repeaters, an intermediate `telegraph repeater, a telegraph path interconnecting said terminal repeaters extending through said intermediate repeater, means in said system for transmitting polar telegraph communication signals from said terminal repeaters toward said intermediate repeater, means in said systems for transmitting a first and a second communication signal each of the same polarity but each oi different magnitude from said intermediate repeater toward'said terminal repeaters and a monitoring circuit bridged directly to said intermediate repeater for monitoring on signals transmitted over said system.

2. In a type B polarential telegraph system, an intermediate telegraph repeater, a local monitoring circuit bridged directly to said intermediate 16 repeater, means in said local circuit for receiving signals transmitted through said system, and means in said circuit for transmitting signals from said circuit to said system.

3. In a polarential telegraph system, an intermediate telegraph repeater, means in said repeater for transmitting telegraph communication signals of different magnitudes and of the same polarity to a distant repeater, means in said repeater for receiving polar telegraph signals from said distant repeater, a local telegraph monitoring circuit bridged directly to said intermediate repeater, means in said local circuit for receiving signals transmitted through said intermediate repeater, and means in said local circuit for transmitting signals of the same polarity and of two different magnitudes through said intermediate repeater to said distant repeater.

4. An intermediate telegraph repeater, means connected to saidV repeater for impressing polar telegraph signals on said repeater, means in said intermediate repeater for transmitting two telegraph communication signals each of the same polarity and each of a different magnitude Ain response to said impressed signals, a local monitoring circuit bridged directly to said repeater, a telegraph receiving relay and a telegraph transmitting relay in said monitoring circuit, means connected to said repeater for operating said receiving relay in response to said signals impressed on said repeater, and means in said monitoring circuit for transmitting two communication signals each of the same polarity and each of a diiferent magnitude from said transmitting relay through said intermediate repeater.

5. A direct current telegraph repeater system comprising an intermediate telegraph repeater, a rst means for receiving polar signals in said repeater from a first distant repeater, a second means for transmitting a signal current of a first magnitude and a signal current of a second mag nitude, different from said first magnitude, both of said currents of the same polarity, from said intermediate repeater to a second `distant repeater in response to said received signals, a monitoring circuit bridged directly to said intermediate repeater, teletypewriter transmitting and receivingV means in said monitoring circuit, means for operating said teletypewriter receiving means in response to said polar signals received by said intermediate repeater, and means responsive to the operation of said teletypewriter transmitting means for transmitting a signal of a rst magnitude and a signal of a second magnitude, different from said first magnitude, both signals of the same polarity, through said intermediate repeater to each of said distant repeaters simultaneously.

6. A system in accordance with claim 5 including means for operating said teletypewriter receiver in response to signals transmitted from said teletypewriter transmitter also.

7. A system in accordance with claim 5 including also additional means for transmitting signals from said monitoring circuit to both of said distant repeaters, said additional means comprising a manually operable telegraph key.

8. A system in accordance with claim 5 including also additional means for receiving signals in said monitoring circuit, said additional means comprising a telephone receiver.

9. A system in accordance with claim V5 including an additional telegraph signal transmitter in said monitoring circuit, and means for operating a telegraph receiving device in said monitering circuit in response to the operation of said additional transmitter.

10. In a direct current telegraph signal repeater system, an intermediate telegraph repeater, a local telegraph signal transmitting and receiving monitoring circuit bridged directly to said intermediate repeater, a telegraph signal receiving relay in said monitoring circuit, a biasing winding on said relay, a rst line winding on said relay connected to a telegraph line extending in a rst direction from said intermediate repeater, a second line Winding on said relay connected to a telegraph line extending in a second direction from said intermediate repeater, and means interconnecting said line windings and said repeater for energizing said second winding when a signal is received from said first line to reproduce said signal in said monitoring circuit.

11. In a direct current telegraph signal repeater system, an intermediate telegraph repeater, a local telegraph signal transmitting and receiving monitoring circuit to said intermediate repeater, a telegraph signal receiving relay in said monitoring circuit having a flrst line winding connected directly to a line connected to a rst side of said repeater and a second line winding connected directly to a line connected to a second side of said repeater, means for transmitting a spacing signal through said second winding in response to a spacing signal received from said rst line, and means for transmitting a spacing signal through said first Winding in response to aspacing signal received from said second line.

12. In a direct current telegraph signal repeater system, an intermediate telegraph repeater, a local telegraph signal transmitting and receiving monitoring circuit bridged directly to said intermediate repeater, a telegraph relay in said monitoring circuit, three windings on said relay, two of said windings connected directly to lines connected to said intermediate repeater, means for transmitting current through each of said windings, each of said currents having an effect tending to operate the armature of said relay in the same first direction for a iirst signaling condition received by said repeater, and means for reversing the eiect of current in each of said line windings in response to a signal received from one of said lines for a second signaling condition received by said repeater.

RICHARD B. HEAR/N. CARLETON B. SUI'LIFF.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS 

